This invention relates generally to mechanism for low power, short range wireless device communication. Such a system improves upon existing proposed Bluetooth low-energy specifications. In particular, the present invention relates to systems and methods for improving directed connectable advertising, and improved scanning by Bluetooth devices. Such systems and methods provide a number of benefits, including more rapid connectivity between devices, and accordingly a much lower power consumption rate. This enables devices to run for extended periods of time, or reduces the size of the power source required by these devices.
Bluetooth is an open wireless technology standard for short distance device communication. Bluetooth devices use short wavelength radio transmissions in the Industrial, Scientific and Medical (ISM) channel from 2400-2480 MHz. Bluetooth uses frequency-hopping spread spectrum, which chops up data into chunks which are then transmitted on up to 79 channels, each 1 MHz (for classical Bluetooth) or 40 channels, each 2 MHz (for low energy Bluetooth) centered from 2402 to 2480 MHz. Bluetooth is a packet based protocol with a master-slave structure. The master may communicate with multiple slaves and each device shares the master device's clock.
Bluetooth technology has changed and adapted as consumer demands have evolved. “Classical Bluetooth technology” typically refers to Bluetooth Version 2.1+EDR (Enhanced Data Rate) and Version 3.0+HS (High Speed) specifications. Recently Bluetooth low energy specifications have been introduced. Classical Bluetooth technology and low energy technology share a number of commonalities: they are both low cost, short range, interoperable robust wireless technologies. However, there is a critical difference between these technologies, Bluetooth low energy is designed as an ultra low power (ULP) technology.
Many modern devices require a very long service life without battery replacement. Others have limited size or weight availability, thereby requiring reduced power supplies. Thus there is a consistent and powerful drive toward minimizing power load requirements in these devices. Bluetooth low energy was designed to meet some of these needs. This enables a new class of low cost Bluetooth products with very long battery life, such as fitness sensors, proximity key fobs, and wireless watches.
Bluetooth low energy enables devices to be aware of one another but not be connected most of the time. In some modes of operation, only when absolutely necessary do the devices link to one another, and then the connection is maintained for as short a duration as possible. In other modes of operation, Bluetooth low energy is also capable of connections of longer duration, more similar to that of classical Bluetooth. Classical Bluetooth technology is connection oriented, with a fixed connection interval. This is ideal for high activity connections, such as mobile phone linkage to a headset. However, such an active connection requires more frequent transmissions, which drains power at a much faster rate.
Bluetooth low energy technology is ideally suited for the transmission of data from compact wireless sensors, or other peripherals, where fully asynchronous communication can be utilized. These devices send low volumes of data (i.e., a few bytes) infrequently (i.e., a few times a second at most).
Bluetooth low energy employs two multiple access schemes: Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA). Forty physical channels, separated by 2 MHz, are used in the FDMA scheme. Three of these channels are used as advertising channels, and the remaining 37 are used as data channels.
The physical channel is sub-divided into time units known as events. Data is transmitted between low energy devices in packets that are positioned in these events. There are two types of events: Advertising and Connection events. This application will be centered about advertising events and as such, for the sake of clarity, the discussion will center about this event.
Devices that transmit advertising packets on the advertising physical channels are referred to as “advertisers”. Devices that receive advertising on the advertising channels without the intention to connect to the advertising device are referred to as “scanners”. Transmissions on the advertising physical channels occur in advertising events. At the start of each advertising event, the advertiser sends an advertising packet corresponding to the advertising event type. Depending on the type of advertising packet, the scanner may make a request to the advertiser on the same advertising physical channel which may be followed by a response from the advertiser on the same advertising physical channel. The advertising physical channel changes on the next advertising packet sent by the advertiser in the same advertising event. The advertiser may end the advertising event at any time during the event. The first advertising physical channel is used at the start of the next advertising event.
An advertiser uses an advertising procedure to perform unidirectional broadcasts to devices in the area. The unidirectional broadcast occurs without a connection between the advertising device and the listening devices. The advertising procedure can be used to establish connections with nearby initiating devices or used to provide periodic broadcast of user data to scanning devices listening on the advertising channel. The advertising procedure uses the advertising physical channel for all advertising broadcasts.
Correspondingly, a scanning device uses a scanning procedure to listen for unidirectional broadcasts of user data from advertising devices using the advertising physical channel. A scanning device can request additional user data from an advertising device by making a scan request over the advertising physical channel.
Bluetooth devices use the advertising procedure and scanning procedure to discover nearby devices, to be discovered by devices in a given area, or to form a connection with another Bluetooth device. The discovery procedure and connection procedure are both asymmetrical. A first Bluetooth device needs to listen for devices advertising scannable or connectable advertising events, while another Bluetooth device is actively broadcasting scannable or connectable advertising events over the advertising broadcast physical channel. For more information on low energy Bluetooth see “Bluetooth Specification Version 4.0 [Vol 0]”, published Jun. 30, 2010, which is hereby incorporated by reference.
While current low energy Bluetooth protocol goes a long way in reducing the required energy used to establish connections, there is always a demand to further reduce power usage, reduce the connection establishment time, ensure more consistent connection establishment, and provide flexibility scheduling advertising transmissions. In particular, it would be highly advantageous to be able to optimize the advertising protocol and scanning protocol to ensure fewer advertising transmissions and more rapid connection establishment as these will limit the amount of time a device is utilizing the radio frequency (RF) transceiver (the largest burden on power consumption). The advertising may also be enabled to periodically transmit for longer time periods than traditional modes of operation, therefore increasing connection establishment reliability. Further, if these optimizations may be effectuated without unduly complicating the Bluetooth devices, or increasing component costs, and be backwards compatible with Bluetooth 4.0 specifications, such optimizations to further reduce power requirements would be of particular value.
It is therefore apparent that an urgent need exists for a system and method for improving low power short range wireless communications. In particular, the need exists to optimize the advertising and scanning procedures of low power Bluetooth devices to further reduce power consumption through more efficient connections. Such a system and method would enable devices to run longer or have a smaller power source, thereby reducing user need for replacement of power (increased convenience) and enabling smaller and lighter wireless devices.